Transverse torque arm - Advice needed

[Jeff.Sloan]

I bought my 2004 630 from Ray_nomad several months ago. After buying, I had it inspected and the local truck mechanic said the transverse torque arm had failed (bushings) and needed to be replaced. I ordered one from Volvo and am finally getting around to replacing it:

 

However, I am starting to worry that something larger might be a problem. The transverse torque arm that is in the truck has a significant amount of twist on the bushings, as if the axle is too far forward. The truck was singled short, initially with the wrong rear leafs. Ray later purchased the correct rear leafs with the correct angle for the driveshaft alignment. Truck runs great but there is heavy side loading on the transverse torque arm mount bolts and I am afraid someitng else is wrong and if I remove the old transverse torque arm I won't be able to get the new one into position.

 

 

Anyone replace one of these before? Is it supposed to have this much twist on it? If not, what would likely cause this? Any advise before I tear this thing apart and can't get it back together would be greatly appreciated.

 

Thanks

Jeff

 

EDIT: Full size pics here: http://nicoleandjeff.net/tta/

[Ronbo]

Does your new arm have that twist in it?

[MrSeas]

Try Inflating / deflating the rear suspension air bags and see what that does. Often times it will help with the R&R of the Torque Arm.

[Scrap]

The tower is cast for 13 deg like it was when it was in the back. It needs to be cut off and the 2-4 deg one welded on. But easier said than done...... Probably just make sure truck is at correct ride height and axle is parked happily centered. Then remove frame bracket, set it straight across the axle where it wants to be, then transfer punch and drill. By rights it should be aligned again to recheck offset so you can shim the new offset, depending on how perfect you want to be.

 

Nice pic by the way-no misunderstandings on that one!

[Jeff.Sloan]

Thanks for the help so far. I was afraid something wasn't right! Sorry, dumb question, when you say "tower", which part are you referring to?

 

I think I will just relocate the frame bracket. Sounds like the easier solution.

 

Let the drilling project commence (tomorrow)!

[billr]

Scrap has it for ya. When they singled and moved the rear fwd they had to relocate the arm mount up the rh side as the original front axle mounts opposite up the left.

 

When they altered later the angles it loaded the arm.

 

Moving the mount over should fix.

 

You may have to plate the outside of the frame with a piece of 3/16 or 1/4" then re drill if the holes are too close. Not too big a job though.

[Jeff.Sloan]

Thanks. This all makes sense now. I found this diagram online as well which helped me understand what it used to look like:

https://patentimages.storage.googleapis.com/US6793225B2/US06793225-20040921-D00003.png

 

I will work on this today. Thanks for the tip on plating the frame if needed. I had not thought of that :-)

[HERO Maker]

What does it look like when you are inflated, or deflated? And you said leaf springs??? No air springs?

[rickeieio]

Rocky, looking at the first pic, he has air springs. He's probably refering to the arched arms to which the axle housing is fastened. They likely have a technical name........ On a motorcycle it would be a swingarm.

[HERO Maker]

I see that now Rick.

When I replaced mine, it was difficult, but I just worked the air leveling valve (since I was replacing it also) and it made the process pretty easy.

[Jeff.Sloan]

It looked pretty much the same when air was applied. Yes, air springs, I should have called them trailing arms (that's what they are called in four wheeler world).

 

After a few hours, several drill bits, a sore back (drilling six holes while straddling an axle is not fun), and a few choice words, here is the finished product:

 

Thankfully no frame plating was needed. So now that I fixed it I'm curious: will this help with fuel economy or tire wear or anything good like that - or does it just stop the truck from tracking funny as it goes down the road?

 

Thanks again for the help!

[I'mdonewiththis forum]

The purpose of that torque arm is just to keep the axle from walking sideways. The 'swing arms' as you called them keep the axle in place front to back.

[Scrap]

Volvos calls them z-springs. Peterbilt calls them air leaves. KW doesn't use them so they don't really have a name. The axle tower is that casting welded to the top of the axle. I have no idea what improvements it'll make but let us know!

[jkennell]

Am I the only one who thinks that may cause binding? Axle travels basically up and down. That torque arm is going to try to force the top of axle to move forward when up, back when down (referenced to the frame). Maybe enough give in the bushings, and short enough travel, to not be a problem, but the angle of motion of the arm and axle are sure different....

[rickeieio]

Wow. How did we all miss that one? Something is amiss on the differential side of the arm, then the holes need to be re-drilled. Unless it's trick photography......

[HERO Maker]

Yes, it appears on the before shots that the attachment to the frame is a little bit aft of the center of the axle. But on the after shots it looks like it is straight above the axle. It could just be the angle from where the picture was taken, but I keep seeing it directly above the axle and not 1 to 2 inches to the rear of it.

[rickeieio]

I think, (Dangerous territory) Jeff is pointing out that the arm is rolled back, perhaps as much as 30-45 degrees. Yes it's parallel to the axle, but vertical movement of the axle will cause fore-aft movement of said axle, or flexing of the arm/bushings.

 

Not good, if the picture is accurate.

[jkennell]

Precisely. the angle of the pivot pins on the arm is not the same as the angle of motion of the axle.

 

Scrap pointed this out above, that the back axle had a 13 degree tower, rather than 2-4 degree like needed on the front. So i'm guessing that the angle is off 10 degrees. Looks worse in the pictures!

 

This MAY not be a problem in actual use...the rubber bushing may have enough give that the arm will simply twist slightly on the bushings up to down. Which may be why Scrap said it will probably be fine. Also, most of the time the arm will be at the "rest" position during operation (normal ride height) The worst twist will only be when dumped (stopped).

 

I'd most likely go with Scrap..."it'll work". Just pointing out it isn't "right" and MAY cause issues. I would definitely operate the suspension thru the dumped to ride range, and make sure it doesn't seem to be trying to twist/ break anything when dumped. (what kind of leverage will this put on the Z-Springs?) If everything looks OK, no major creaking or twisting evident, still some give in the torque arm bushings, I'd just run it. Better than way back like before!.

[Jeff.Sloan]

I'm not an expert, but I don't think it's an issue. With the air fully dumped, it looks basically the same. There is a good amount of rubber in the transverse torque arm end bushings. If it could flex backwards as much as it was in the 'before' photos, then it should be able to flex a bit as the axle goes up and down.

 

Thinking of this another way - How are other singling jobs done? Is the forward-rear axle tower normally cut off and re-welded to the rear-rear axle? I imagine they would be done the easy way - just like mine was (although the wrong trailing arms/Z arms were used initially).

 

Here are some new photos with no air in the truck at all (been parked for a week):

 

After driving it last weekend, the rear did feel a little tighter/more solid. Not sure if this was a real difference or the empty wallet justification bias . . .

[Scrap]

Yea, it isn't perfect but "it'll work". Not perfect because it isn't parallel to the axle but better than it was. Perfect would be a new tower cast to the right angle. The rod looks kind of tweaked like it might have already bound once before or something big got dropped on it or something but it could be the pics too.

[Jeff.Sloan]

Thanks for opining. Good enough for Rock and Roll!

 

Regarding the apparent bend, I see what you mean. That's a photo angle effect. The arm is brand new from Volvo dealer.

[jkennell]

Perfect would be a new tower cast to the right angle.

 

Hmm--just for the sake of "thinkin"...that particular bracket just looks like a bent steel U, welded to the axle housing and the steel sleeves the arm bolts to. Couldn't you make a sawzall cut about 1/2 way down the long leg of the U, overlap the cut piece outside the original plate, and reweld top and bottom of the overlap? (Make sure to keep the right spacing!) If you did it right you could get any angle you wanted. Seems like an easy fix that would not even weld on the axle itself.

 

Or isn't that fabed steel like it looks?

[Broncohauler]

Looks good to me nice job.

If you don't have any vibration and it tracks straight I'd say your good?

You could always put a angle finder on the pinion and check your readings at full deflation and full ride night?

[Jack Mayer]

Here is the plate on the back of the torque arm on my new truck. We just finished singling it. LINK.

 

If you want video, HERE is the link.